Introduction
One of the most essential aspects of proper body function is breathing air. The fact that the cleanliness and quality of the air we breathe have a direct impact on humans and animals has been proven by numerous studies. Air pollution is one of the major issues according to the World Health Organization (WHO) and is also regulated by various countries. Furthermore, the quality of air does not only affect the health of the people but also our performance. This is particularly true in industrial places where high performance is required. Poor air quality can harm the performance of workers. Healthy outdoor air consists of approximately 78% nitrogen, 21% oxygen and one percent other gases and water vapour.
After a short period, the concentration of carbon dioxide in an enclosed space can reach levels that have a measurable and demonstrative effect on a person’s ability to concentrate. It can be shown that the amount of errors done will increase in relationship to CO2 concentration, impairing decision making abilities. Concentration of air particles is also known to reduce performance. This overall reduction in workers’ performance generates unnecessary stress for workers inside of the organisation. According to a study, researchers from Harvard University led by Jose Guillermo Cedeño Laurent, examined a total of 302 people from six countries that worked in offices for over a year. Their workplaces were equipped with environmental sensors that measured the concentration of fine dust (particle size 2.5 micrometres), carbon dioxide, temperature and humidity in real-time. The cognitive abilities of the workers were regularly checked by a special app. The result concluded that work performance decreased with higher concentrations of fine dust and carbon dioxide. Specifically, an increase in the concentration of fine dust by ten micrograms per cubic meter of air led to one percent slower and less accurate responses in the cognition test. For carbon dioxide, a relatively normal increase of 500 ppm (parts per million) negatively changed thinking skills in a similar proportion.
The following table will help to get an idea about CO2 values:
| CO2 |
Definition |
| 200000 |
Rapid onset of unconsciousness; death |
| 100000 |
Nausea, unconsciousness, vomiting; extinguishing of a candle |
| 30000 |
Breathing rate and volume of breaths increase |
| 6000 |
Health concerns; exposure should be short term; other sensitivities occur |
| 5000 |
Max. Workplace concentration; limited stay of max. 8 hours daily |
| 2000 |
Risk of infection increases |
| 1500 |
Max. Indoor guideline value Fatigue and drowsiness may set in |
| 1000 |
Comfort limit according to Pettenkofer still acceptable in terms of air hygiene |
| 600-800 |
High indoor air quality |
| 350-450 |
Fresh, natural ambient air |
CO2 levels and their definitions in ppm (parts per million)
Aim and motivation
Since we will probably work in offices in the future and are affected by the problem described above, we want to investigate the problem with the help of a real practical example. So we can apply what we have learned with our future employers. We want to present the data in a meaningful way and analyze the results. For this purpose, the company GKS - an architectural office - provides us with their air quality data for a whole year. They have placed a total of six Air-Q sensors in their rooms, which measure the air every two minutes and record it in a database. The office has two floors, each with a larger office and various meeting rooms.
Location of measuring device and plants in the first floor office (Office 1)
Location of measuring device and plants in the second floor office (Office 2)
Both floors are quite similar in structure and size, it is noticeable that there are more plants on the lower floor.
Data analysis
In the data processed by us, one finds over the period of 2022: The CO2 content which is in ppm (parts per million). The TVOC is composed by the VOC (Volatile Organic Compounds) and the TVC (total viable count). In our case, it represents the organic particulate matter in the air. The temperature inside the room is in Celsisus. The performance is a variable composed of Air-Q that reflects mainly the CO2 and the TVOC. Air-Q’s sensors store their readings in their database every two minutes. Another important factor for us are the plants in the room because they convert CO2 back into oxygen through photosynthesis.
Thanks to the measuring devices that report a high CO2 value, the employees of GKS are thaught to ventilate in case of poor air quality. The TVOC and CO2 values often do not rise at the same rate, but there is a correlation seen between their increases. In a general overview, the CO2 content in the air from August 2022 is shown monthly over the year.
Average Monthly CO2 Concentration in Open Office 1
It is noticeable that the CO2 value in winter is not as low as in summer because there is less ventilation to maintain the room temperature than in summer.
There are extreme values frequently encountered, particularly in smaller meeting rooms. Due to the indication of the measuring devices, in most cases, the GKS employees let some fresh air into these rooms during the meetings.
Extreme values in a meeting room (CO2, TVOC & Temperature)
Ventilation has a strong influence on the CO2 and TVOC concentration in the air. It improves the air quality a lot in a short period within rooms. However, especially in winter, ventilation affects not only the air quality but evidently also the temperature. It also happens from time to time that, despite good readings on the measuring devices, airing is forgotten and nothing can be done about it.
Although, ventilation has by far the greatest influence. The plants also have a considerable amout of effect on the CO2 concentration in the air.
CO2 distribution in the office 1&2 over the year 2022
It is interesting to see how much difference a few plants can make because the difference between the two offices is significant. Almost over the entire year, the CO2 value of the first floor is smaller than that of the second floor, which had fewer plants. As a reference point, we can mainly take the hours in the morning because there are no people that affect the data. The difference between CO2 and TVOC levels is also noticeable during lunch time since all employees have lunch on the first floor. However, the exact opposite is the case with TVOC. Plants and animals constantly emit organic particles into the ambient air. Therefore, the TVOC on the first floor is constantly higher than on the second floor.
TVOC distribution in the office 1&2 over the year 2022
In this figure, the morning is particularly of interest. Between 7:00 and 9:00, the TVOC value of the first floor is significantly higher than that of the second floor. The answer to this can be found in the temperature. It suggests that the second floor is ventilated significantly more than the first floor at this time.
Temperature distribution in the office 1&2 over the year 2022
To achieve the goal of the best possible work environment through air quality, Air-Q has created a performance value which is composed of the TVOC and CO2 values.
This correlation is shown quite well on the second floor. Since TVOC does not change much throughout the day except for the morning, the performance value is usually inversely proportional to the CO2 value. However, based on the morning hours, it can be seen that TVOC has a strong impact on employee performance. In the following statistics, all values of the two offices are summarized again.
Measurements overview from office 1 and office 2 over the year 2022
Findings
Based on the difference in the performance value it can be seen that the office on the second floor is doing much better than the one in the first floor. The main reason for this is mainly the ventilation in the morning. The effect of the plants is mainly noticeable towards the afternoon, but in this small scale a few smaller indoor plants can not change too much.
However, it is also important to notice not to rely too heavily on this one value and not to ventilate the room just because the Air-Q only displays the CO2 and the performance value. GKS is an example for good air quality in the office due to its equipment. It can be much worse in other offices. For our future, we take notice that indoor rooms should be ventilated at least once a day, and preferably even twice if it is heavily used. Also having plants in the office can help the concentration and performance of employees. Thanks to our new findings, we can further optimize our performance and better adapt to moments that require full commitment.